\name{fish.length}
\alias{fish.length}
%- Also NEED an '\alias' for EACH other topic documented here.
\title{ Prepare a length data table }
\description{ Use a length matrix to produce an object of type
  \code{fish.length} }
\usage{
fish.length(data, ncol = c(1, 2, 3, 4))
}
%- maybe also 'usage' for other objects documented here.
\arguments{
  \item{data}{ Data matrix with year, zone, sex and length }
  \item{ncol}{ A vector with the position of columns year, zone, sex and
    length }
}
\details{
  In fish biology the most common data recorded is weigt and length.
  This function use a data matrix and generate an object to be used with
  an age length key and transform a frequency distribution of length
  into a frequency distribution of age.
  \code{fish.length} Sort the information of sex and length for each
  year and zone. It generate an object that contain the data and a
  summary table.
}
\value{ An object of \code{\link[base]{class}} \code{"fish.length"}, it
  is a list with:
    \item{length }{Data table with the next columns
	    \item{year }{Year of data colection}
	    \item{zone }{Column identifing the origen zone of the 	organism}
	    \item{sex }{Column identifing the sex of the measured fish}
    	\item{length }{Length recorded of the organism}
	  }
  \item{frec.Table }{Frecuency table of fishes for earch year and zone}
  
}
\author{Jorge Cornejo-Donoso}
\note{This must be tested, please use it carefylly}
\seealso{This is like \code{\link{fish.age}}}
\examples{
  \dontrun{
    ##library(ialk)
    ##length <- fish.length(matrix.length,ncol=c(2,4,3,1))
    ##print(length)
	   }
	  }
\keyword{misc}
